The humoral immunity of patients with malignant tumors of the central nervous system will be studied using an established in vitro microcytotoxicity assay. A longitudinal study using both autologous and allogeneic tumor cells will be carried out to determine the frequency of complement dependent cytotoxic antibodies in patients with varying tumor loads. Sera from these patients will be fractionated in to IgG, IgM and IgA classes to determine the immunoglobulin class of the cytotoxic antibodies and how the class might change with changes in the biological behavior of the tumor. Patients with other tumor and non-neoplastic central nervous system disease as well as normal persons will be tested for the presence of these antibodies. Serial absorptions will be carried out to determine the specificities of the cytotoxic response. The methodical examination of the humoral response of patients with central nervous system tumors will lead to refined techniques for the immunodiagnosis and serological monitoring of these patients.